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Several factors pointed toward al-Qaida as being responsible for the simultaneous bombings Thursday that killed at least 192 people and injured 1,240 others in Madrid, Spain.

The London-based Arabic newspaper al-Quds al-Arabi said it received a claim of responsibility issued in the name of al-Qaida from the Brigade of Abu Hafs al-Masri. The Brigade, named for the late top lieutenant to senior al-Qaida figure Ayman al-Zawahri, claims to be affiliated with Osama bin Laden’s terrorist network, which is blamed for the Sept. 11, 2001, attacks that killed nearly 3,000 people at the World Trade Center and the Pentagon.

U.S. officials told NBC News that a statement Oct. 18 from bin Laden specified Spain as a potential al-Qaida target, among other members of the U.S.-led coalition in Iraq.

Unprecedented operation
The claim by the Brigade of Abu Hafs al-Masri could not immediately be given full credence. Its claim last year to have been responsible for the widespread power blackout in the Northeast and Canada last Aug. 14 was discredited.

Another senior U.S. official also cautioned that “after an attack like this, all sorts of people claiming to be al-Qaida come out of the woodwork. ... We simply do not know yet.”

White House spokesman Sean McCormack said, “We’ve seen the news reports, and we’re going to determine what the facts are.”

But the level of sophistication exhibited in the Madrid bombings — virtually unmatched in the history of terrorism — indicated that only al-Qaida had the scope of operations capable of committing them.

Only once before has a terrorist strike used as many bombs, an attack in February 1993 that killed 260 people in the financial district of Bombay, India. That attack was carried out by Muslim extremists led by a crime lord who eventually was linked to bin Laden.

Authorities said the attack Thursday was far more sophisticated. While the 13 bombs that exploded in Bombay detonated over 2 hours and 28 minutes, the 10 in Madrid all blasted in less than a half-hour, indicating significantly greater planning and execution.

Pattern of al-Zawahri statements
If the attacks Thursday were carried out by al-Qaida, it would be at least the sixth time in six years that a statement by al-Zawahri had been followed by a significant al-Qaida attack within three weeks, according to an NBC News analysis of the statements.

U.S. intelligence officials told NBC News on condition of anonymity that U.S. security officials took any such pronouncements seriously and studied them for possible “go signals” instructing al-Qaida operatives to carry out attacks.

The most recent messages came Feb. 24, which would continue the pattern. Al-Zawahri taunted President Bush in two broadcast tapes and challenged assertions in the president’s State of the Union address that Iraq had been liberated and that al-Qaida was on the run in Afghanistan. He also assailed France for its recent ban on the wearing of Muslim head scarves at public schools.

On one of the tapes broadcast last month, al-Zawahri, 52, said al-Qaida was “still in the holy war battleground” and vowed to carry out more attacks against the United States.

“Bush, fortify your targets, tighten your defense, intensify your security measures,” the voice warned, “because the fighting Islamic community — which sent you New York and Washington battalions — has decided to send you one battalion after the other, carrying death and seeking heaven.”

Other attacks that closely followed statements by al-Zawahri were:

On Aug. 6, 1998, al-Zawahri sent a statement to a London-based Arabic newspaper saying, “We are interested in briefly telling the Americans that their messages have been received and that the response, which we hope they will read carefully, is being readied.”

The next day, suicide bombers detonated bombs at the U.S. embassies in Nairobi, Kenya, and Dar Es Salaam, Tanzania, killing more than 220 people. Al-Qaida claimed responsibility.

On Oct. 9, 2002, a tape from al-Zawahri threatened attacks on the United States, its economy and its allies. “I promise you that the Islamic youth are preparing for you what will fill your hearts with horror,” al-Zawahri said.

Three days later, bombs destroyed a nightclub in Bali in Indonesia, killing more than 200 people, most of them Westerners. Officials in the United States, Australia — which lost many citizens in the attack — and Indonesia said al-Qaida financed the attack.

A suicide bombing of the USS Cole in Aden harbor in Yemen killed 17 U.S. sailors on Oct. 12, 2000, three weeks after the release of a tape in which al-Zawahri, bin Laden and Rifai Taha of the Egyptian Islamic Group warned of imminent attacks.

A suicide bombing of a bus carrying French naval experts in Karachi, Pakistan, killed 14 people on May 8, 2002, three weeks after a videotape was released in which al-Zawahri and bin Laden were seen speaking along a river in Afghanistan. Also seen on the tape were “martyr’s wills” of previous suicide bombers.

A suicide bombing attack on German peacekeepers in Kabul, Afghanistan, killed four people and wounded 31 others on June 7, 2003, two weeks after an audiotape attributed to al-Zawahri aired on various radio and television outlets in the Middle East.

Assassination bids followed criticism of Musharraf
In addition, Zawahri was heard on an audiotape last Sept. 29 calling Pakistani President Pervez Musharraf a “traitor” for helping U.S.-led forces topple the Taliban regime in Afghanistan, for considering a U.S. request to send peacekeeping troops to Iraq and for weighing diplomatic recognition of Israel.

On Dec. 14 and again on Christmas Day, assassins believed to have been affiliated with al-Qaida tried to kill Musharraf as he drove in his motorcade, first in Rawalpindi and then in Islamabad.

A U.S. intelligence official told NBC News that a call to arms from al-Zawahri that aired Dec. 19 was a key factor in the decision to raise the U.S. threat level assessment from “yellow” — or elevated — to “orange” — or high — two days later.

In that message, delivered to al-Jazeera television, al-Zawahri commemorated the second anniversary of the battle of Tora Bora in Afghanistan with a call for more attacks on Americans, including in the American “homeland.”

U.S. officials said after returning the threat assessment level to “yellow” in January that it was unclear whether the heightened state of alert had averted a planned attack.

Robert Windrem is an NBC News producer based in New York. Charlene Gubash is an NBC News producer based in Cairo, Egypt. NBC’s Andrea Mitchell, in Washington, and MSNBC.com’s Alex Johnson contributed to this report.